I have Bees Jubilee that I ordered bare root online.

It stayed in a 2-gallon container for two winters before I was able to finally plant in the ground this spring.

Yes, you can pot it for this year, or keep it potted forever if the pot is big enough.

Today I bought a Belle of Woking and Nirobe that were in tallish, skinny, plastic containers at the nursery. The foliage was healthy and I transferred them to 2 qt containers because those are the largest I have on hand.

What size containers do I need if I want to keep them in pots this season, as I work on the soil around my new house? How often should I cut back the top growth? I am so excited to finally grow these!

I personally prefer 1 gallon sized pots for growing out clematis. The larger the pot, the less the watering in the heat in my zone. That may not be as much of an issue in your zone.

As far as how tall to allow the clematis to get before trimming is entirely up to you and what you want or expect out of them when they are in their containers. Personally however, I would pinch out growing tips after you have two or three sets of leaves on any given stem. I would repeat after the side shoots develop and have another 2 to 3 sets of leaves. How many times I did this would depend on the size of the containers, how much I wanted to spend watering, how large the root balls were before potting up, and how fast the plants and their root systems grew over the spring and summer.